A New Genetic Linkage Map of the Zygomycete Fungus Phycomyces blakesleeanus

Abstract

Phycomyces blakesleeanus is a member of the subphylum Mucoromycotina. A genetic map was constructed from 121 progeny of a cross between two wild type isolates of P. blakesleeanus with 134 markers. The markers were mostly PCR-RFLPs. Markers were located on 46 scaffolds of the genome sequence, covering more than 97% of the genome. Analysis of the alleles in the progeny revealed nine or 12 linkage groups, depending on the log of the odds (LOD) score, across 1583.4 cM at LOD 5. The linkage groups were overlaid on previous mapping data from crosses between mutants, aided by new identification of the mutations in primary metabolism mutant strains. The molecular marker map, the phenotype map and the genome sequence are overall congruent, with some exceptions. The new genetic map provides a genome-wide estimate for recombination, with the average of 33.2 kb per cM. This frequency is one piece of evidence for meiosis during zygospore development in Mucoromycotina species. At the same time as meiosis, transmission of non-recombinant chromosomes is also evident in the mating process in Phycomyces. The new map provides scaffold ordering for the genome sequence and a platform upon which to identify the genes in mutants that are affected in traits of interest, such as carotene biosynthesis, phototropism or gravitropism, using positional cloning.

Sex Determination Directs Uniparental Mitochondrial Inheritance in Phycomyces

“…A genetic map of Phycomyces was recently created using nuclear molecular markers in progeny after crossing two wild-type parents (12). Here, oligonucleotide primers were designed to amplify a variable part of the mitochondrial genome (mtDNA) (Fig.…”

Diversity, ecology, and evolution in Phycomyces

“…The restriction-fragment length polymorphisms described by Chaudhary et al (2013) were tested with the primers listed in Table S1.…”

“…Strains NRRL1555 and UBC21, the only wild types whose genomes have been sequenced, differ in these markers localized throughout the genome (Chaudhary et al 2013). The same analyses could not be repeated with Phycomyces nitens because of insufficient conservation of the DNA sequences.…”

“…Nearly all laboratory research has been done with P. blakesleeanus strains of unknown origin, particularly the standard strain NRRL1555, whose complete genome has been available since 2006 (Joint Genome Institute, US Department of Energy). The genetic analysis of Phycomyces differs notably from that of other organisms, but has led to recombination maps of phenotypic (Orejas et al 1987) and molecular markers (Chaudhary et al 2013).…”

Early and Late Trisporoids Differentially Regulate β-Carotene Production and Gene Transcript Levels in the Mucoralean Fungi Blakeslea trispora and Mucor mucedo

“…Finally, gametangia bearing two nuclei from opposite partners fuse to form a thick-walled dikaryotic sexual spore known as the zygospore. Mitosis followed by meiosis results in four haploid products in a sporangium that develops from the zygospore (3). One Mucorales species in particular, Blakeslea trispora, has been commercially exploited for its potential to produce an excess of carotenoids, like ␤-carotene and lycopene, during its sexual phase of the life cycle (4,5).…”